What is network monitoring?

Network monitoring is the continuous collection, analysis, and alerting on the health and performance of network infrastructure. It typically combines SNMP polling (querying device metrics at set intervals), ICMP probing (availability checks), flow analysis (NetFlow, sFlow, IPFIX for traffic visibility), and SNMP traps (event-driven alerts from devices). Good network monitoring directly reduces MTTR by surfacing issues before users notice them, supports capacity planning by trending interface utilisation, and provides evidence for compliance audits. The core question when choosing a tool is whether it gives your team the right data, in the right format, with alerts they can actually act on.

Tool Comparison — 2026

The following table compares the six most widely deployed network monitoring platforms across criteria that matter for a real production environment.

Tool Free Tier Deployment SNMP Support Flow Analysis Alerting Best For UK Support
PRTG 100 sensors On-prem / Cloud v1, v2c, v3 NetFlow, sFlow, IPFIX Email, SMS, push, HTTP SME and mid-market Windows environments Paessler resellers
Zabbix Fully free On-prem v1, v2c, v3 + traps Plugin available Email, Slack, PagerDuty, webhook Enterprise scale, custom integrations Community + commercial
LibreNMS Fully free On-prem v1, v2c, v3 sFlow, NetFlow Email, Slack, PagerDuty, Telegram Network-first teams, fast auto-discovery Community
Nagios Core Fully free On-prem Via plugins Via plugins Email, script-based Mature UNIX environments, plugin ecosystems Community / Nagios XI commercial
Grafana + Prometheus Fully free On-prem / Cloud Via SNMP exporter Via exporters Alertmanager (email, Slack, PD, OpsGenie) Observability-first orgs, unified dashboards Grafana Labs (UK office)
SolarWinds NPM No free tier On-prem v2c, v3 + traps NetFlow, sFlow, IPFIX, J-Flow Email, SMS, push, ticketing integrations Large enterprise, vendor support required SolarWinds partner network

What to Look For When Choosing

Before committing to a platform, evaluate it against these technical criteria for your specific environment:

SNMP v2c vs v3

SNMP v2c is community-string based — effectively cleartext authentication. SNMP v3 adds authentication (MD5/SHA) and encryption (DES/AES). Any network monitoring deployment in 2026 should use v3 unless legacy device constraints prevent it.

Trap Handling

SNMP traps let devices send alerts proactively (link down, fan failure, threshold breach). Check whether the tool has a built-in trap receiver, supports custom MIB loading, and can correlate traps with polled metrics in the same alert.

NetFlow / sFlow Support

SNMP gives you interface utilisation — flow data (NetFlow v5/v9/IPFIX, sFlow) tells you who is using the bandwidth. Critical for troubleshooting, capacity planning, and detecting unexpected traffic patterns or potential data exfiltration.

MIB Support

Vendor-specific SNMP metrics (Cisco CPU, memory pools, BGP peer state, optical power levels) require the correct MIBs loaded. Confirm the tool supports custom MIB import and can discover and present these OIDs without manual scripting.

Scalability

PRTG and Zabbix both scale to thousands of devices, but architecturally differently. PRTG uses probe servers. Zabbix uses proxy nodes. For environments over 500 devices, test the poller architecture before committing to a platform.

Alert Quality

The best monitoring tool is one your team actually responds to. Evaluate alert fatigue risk — does the tool support maintenance windows, dependency mapping (suppress child alerts when upstream is down), and alert deduplication?

Frequently Asked Questions

What is the best free network monitoring tool?
For most organisations, Zabbix or LibreNMS are the strongest free options. Zabbix scales to very large environments and has enterprise-grade alerting with a rich webhook and integration ecosystem. LibreNMS is easier to get started with, has excellent auto-discovery for Cisco and other network devices, and comes with pre-built dashboards. Grafana + Prometheus with the SNMP exporter is a strong choice if you already have an observability stack and want unified infrastructure and network dashboards.
Does Zabbix support Cisco SNMP traps?
Yes. Zabbix has a built-in SNMP trap receiver (zabbix_trap_receiver) and supports loading Cisco-specific MIBs. You can configure trap actions to trigger high-priority alerts, execute scripts, or auto-acknowledge follow-up events. Zabbix also supports SNMP v2c and v3 polling and ships with pre-built Cisco IOS, Cisco Catalyst, and Cisco ASA templates in its official template library.
What is SNMP polling?
SNMP polling is the process of a monitoring system sending SNMP GET requests to network devices at regular intervals (typically every 60–300 seconds) to retrieve performance metrics — interface utilisation, error counters, CPU load, memory usage, temperature sensors, and more. The device responds with the values for the requested OIDs. This is the pull model. The complementary push model is SNMP traps, where the device proactively sends an unsolicited notification to the monitoring server when a defined event occurs (link state change, temperature threshold breach, etc.).
Is PRTG free for small networks?
PRTG offers a permanent free tier limited to 100 sensors. A sensor monitors one metric — so a single managed switch typically consumes 4–8 sensors (ping, SNMP CPU, SNMP memory, interface traffic per port). 100 sensors realistically covers a small office of around 10–15 devices with basic monitoring. Beyond 100 sensors, a paid licence is required. PRTG is sold perpetually or on subscription, priced by sensor count, and can become expensive at scale compared to free alternatives like Zabbix.

Free Network Config Templates

Download production-ready SNMP configuration templates for Cisco IOS — community strings, v3 user config, trap destinations — from our free template catalog.

Browse Free Templates →